docs: Add toolchain homepage

Bug: 373454866

Change-Id: Iea27fe90e0f3ff0522f5becc9e7ed57d74b3eb72
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/247593
Lint: Lint 🤖 <[email protected]>
Presubmit-Verified: CQ Bot Account <[email protected]>
Commit-Queue: Auto-Submit <[email protected]>
Pigweed-Auto-Submit: Kayce Basques <[email protected]>
Reviewed-by: Amit Uttamchandani <[email protected]>

docs/BUILD.bazel

@@ -43,6 +43,7 @@ sphinx_docs_library(
         "python_build.rst",
         "targets.rst",
         "third_party_support.rst",
+        "toolchain.rst",
     ],
     strip_prefix = "docs/",
     target_compatible_with = incompatible_with_mcu(),

docs/BUILD.gn

@@ -435,6 +435,7 @@ pw_doc_gen("docs") {
     "python_build.rst",
     "targets.rst",
     "third_party_support.rst",
+    "toolchain.rst",
   ]
   output_directory = target_gen_dir
   deps = [

docs/conf.py

@@ -222,7 +222,11 @@ def pygments_monkeypatch_style(mod_name, cls):
 html_baseurl = 'https://pigweed.dev/'
 
 # Hide "Section Navigation" on homepage and changelog.
-html_sidebars = {'index': [], 'changelog': []}
+html_sidebars = {
+    'index': [],
+    'changelog': [],
+    'toolchain': [],
+}
 
 html_context = {
     'default_mode': 'dark',

docs/index.rst

@@ -193,6 +193,7 @@ Talk to us
    Source code <https://cs.pigweed.dev/pigweed>
    docs/showcases/index
    docs/concepts/index
+   Toolchain <toolchain>
    docs/3p/index
    docs/community/index
    Developing & contributing <docs/contributing/index>

docs/toolchain.rst

@@ -0,0 +1,81 @@
+.. _toolchain:
+
+=================
+Pigweed Toolchain
+=================
+Pigweed Toolchain is an LLVM/Clang toolchain for embedded use cases.
+
+.. _toolchain-background:
+
+----------
+Background
+----------
+Our toolchain philosophy is to co-evolve the support for embedded use cases in
+the LLVM project as we onboard new projects to use the Clang/LLVM toolchain
+distributed by us. Teams at Google that we partner with make contributions to the
+LLVM project regularly. Recent contributions include:
+
+* Compiler optimizations
+* LLVM ``libc`` library support
+* Improvements to the LLD linker
+
+.. _live at HEAD: https://abseil.io/about/philosophy#we-recommend-that-you-choose-to-live-at-head
+
+We follow the `live at HEAD`_ model and do all development in LLVM which enables
+us to rapidly adopt new features and provide fast feedback to the LLVM community.
+We continuously build new versions of the Clang toolchain binaries and distribute
+them to our users. Pigweed's toolchain version is periodically updated along with
+code changes necessary to the Pigweed codebase itself to be compatible with and
+take advantage of new toolchain features as soon as they land.
+
+For more information, check out the following presentation:
+
+.. raw:: html
+
+   <iframe width="560" height="315"
+       src="https://www.youtube.com/embed/0HvgvBUPTyw"
+       title="LLVM Toolchain for Embedded Systems"
+       frameborder="0"
+       allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share"
+       referrerpolicy="strict-origin-when-cross-origin"
+       allowfullscreen></iframe>
+
+.. _toolchain-prebuilts:
+
+---------
+Prebuilts
+---------
+.. _CIPD Packages: https://chrome-infra-packages.appspot.com/p/fuchsia/third_party/clang
+
+The toolchain can be downloaded from `CIPD Packages`_. It includes
+a cross-compiler that can target the following architectures.
+
+Embedded targets:
+
+* ARM 32-bit
+
+  * ARMv6
+
+  * ARMv7
+
+  * ARMv8
+
+* RISC-V 32-bit
+
+Host targets:
+
+* Linux
+* Windows\ :sup:`1`
+* macOS\ :sup:`2`
+
+:sup:`1` Contains some limitations around user-side licensing.
+
+:sup:`2` MLInliner is not supported yet.
+
+.. _toolchain-support:
+
+-------
+Support
+-------
+`File a bug <https://pwbug.dev>`_ or talk to the Pigweed
+team on `Discord <https://discord.com/invite/M9NSeTA>`_.